Photosensitive film

ABSTRACT

A photosensitive film excellent in workability and making it possible, in a normal pressure laminating process, to laminate photosensitive films on the surface of substrate having a metallic surface with a reduced number of air voids generated and in a high product yield, said film comprising a support film (A), a photosensitive resin composition-containing photosensitive resin layer (B) formed on said support (A) and a protecting film (C) further stuck on said layer (B), wherein the number of fish eyes having a diameter of at least 80 μm included in the protecting film (C) does not exceed 5 fish eyes/m 2 .

This application is a Divisional of U.S. patent application Ser. No.09/508,771, filed Mar. 16, 2000, which is a National Phase Applicationin the United States of International Patent Application No.PCT/JP98/04184 filed Sep. 17, 1998, which claims priority on JapanesePatent Application No. 09-254816, filed Sep. 19, 1997. The entiredisclosures of the above patent applications are hereby incorporated byreference.

TECHNICAL FIELD

This invention relates to a photosensitive film successfully usable inmetal etching fabrications of lead frame, metal mask, etc.

BACKGROUND ART

In the field of current semiconductor elements, there is a growingtendency of lessening the weight, decreasing the thickness, reducing thesize of elements and manufacturing such elements in a small lot-highvariety manner. As a result of this tendency, the lead frame used formounting IC chips on substrate is required to have an increased numberof pins in a more slender and smaller size. On the other hand, thestamping process is unable to produce such small-sized articlessatisfying the requirement of the miniaturization because of elevatedcost of metallic die needed by the small lot-high variety production.Thus, the etching process is advantageous over the stamping process forthe small lot-high variety production because it can produce small-sizedarticles without using any metallic die. The etching process uses aphotosensitive resin in either of the three forms, namely water-solublephotosensitive resin, solvent-containing liquid photosensitive resin andphotosensitive film.

The use of liquid photosensitive resin has general faults in that anenormous investment must be made in the coating apparatus, the coatingprocess requires considerably much labor, serviceable lives of thephotosensitive resin itself and the coated film of photosensitive resinare short, and sensitivity is low. In addition, individual cases havetheir own faults. For instance, the water-soluble liquid photosensitiveresin in which casein or PVA (polyvinyl alcohol) is cured with a chromicacid salt has a problem that a complicated step of waste water treatmentmust be provided for the disposal of harmful heavy metal salt after use.On the other hand, the solvent-containing liquid photosensitive resinhas a problem that an organic solvent is discharged into the atmosphericair in the course of coating, which exercises an adverse influence uponenvironments.

On the other hand, the photosensitive film has a sandwich structure inwhich a photosensitive resin composition is coated on a transparentsupport film, dried and then covered with a protecting film. At the timeof lamination, the protecting film is removed and at the same time thephotosensitive resin layer is thermally press-bonded to the underlyingmetal to form an image. Accordingly, the photosensitive film is lower inthe cost for equipments, higher in sensitivity and longer in the workinglife than the above-mentioned liquid photosensitive resins, and issuperior in the suitability for metallic precision fabrications.

As the support film of the photosensitive film, polyester films such asPET (polyethylene terephthalate) film are generally used. As theprotecting film, polyolefin films such as PE (polyethylene) film aregenerally used. The protecting film is removed at the time oflamination. The polyolefin film conventionally used as a protecting filmis produced by thermally melting and kneading a raw material and thenforming it by extrusion, biaxial orientation or casting. In general,protecting films of polyolefin or the like include unmelted materials orthermally deteriorated regions called fish eyes. The fish eye usuallyhas a diameter (φ) of 30 to 600 μm, forming a protrusion on the filmsurface up to a height of 2 to 40 μm. The convex portions of the fisheyes are transferred onto the photosensitive resin layer to formconcavities on the photosensitive resin layer, so that air voids 6 areformed on the substrate after lamination as seen in FIG. 1B. That is tosay, if a photosensitive film comprising a support film 1, aphotosensitive resin layer 2 and a protecting film 3 carrying fish eyes4 (see: FIG. 1A) is laminated, after releasing the protecting film 3therefrom, onto a substrate 5, air voids appear as seen in FIG. 1B.Formation of the air voids has a relation with film thickness of thephotosensitive resin layer so that a smaller film thickness ofphotosensitive resin layer causes a more ready formation of air voids.The presence of such air voids causes formation of defective pattern andbreakage of wire in the subsequent steps of exposure, development andetching.

As a means for preventing such phenomena, JP-A 3-12402 discloses the useof a film having a flat and smooth surface as the releasable film at thetime of lamination. The method of JP-A 3-12402, however, ischaracterized by coating a photosensitive resin composition onto areleasable film to be peeled off at the time of lamination and dryingthe coat to form a photosensitive resin layer, followed by laminatingthereon a support film. The releasable film must be selected frommaterials showing no thermal dimensional change when it is coated with aphotosensitive resin composition and dried. In other words, thematerials usable for this purpose are restricted.

Apart from the above, the method of vacuum lamination is useful asmentioned in JP-A 52-66581, JP-A 51-63702, and JP-A 1-314144. Thismethod, however, is disadvantageous in that it needs an apparatus oflarger size as compared with the conventional normal pressure laminationmethod and it tends to generate dusts because inner atmosphere oflamination chamber is kept at a vacuum.

DISCLOSURE OF INVENTION

It is an object of this invention to provide a photosensitive film whichcan be laminated by the normal pressure lamination method on the surfaceof a substrate having a metallic surface in a high product yield, withformation of a reduced number of air voids, and in a high workability.

It is another object of this invention to provide a photosensitive filmexercising the above-mentioned effect of the invention and furtherexhibiting excellent lamination characteristics.

It is yet another object of this invention to provide a photosensitivefilm exercising the abovementioned effect of the invention andexhibiting a particularly high performance when used for metal etchingfabrication of lead frame, metal mask, etc.

This invention provides a photosensitive film which comprises a supportfilm (A), a photosensitive resin composition-containing photosensitiveresin layer (B) formed on said support film (A), and a protecting film(C) stuck onto said photosensitive resin layer (B), wherein the numberof fish eyes having a diameter of at least 80 μm included in saidprotecting film (C) does not exceed 5 fish eyes/m² and saidphotosensitive resin composition-containing photosensitive resin layer(B) has a film thickness of 5 to 30 μm.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1A and FIG. 1B are cross-sectional views illustrating thegeneration of air voids.

BEST MODE FOR CARRYING OUT THE INVENTION

The support film (A) used in this invention is, for instance, apolyester film such as Tetoron Film GS Series manufactured by TeijinLtd., Myler Film D Series manufactured by E. I. Du Pont de Nemours andCo., and the like. Preferably, the support film (A) is a polyethyleneterephthalate film. The support film (A) preferably has a film thicknessof 12 to 25 μm. If thickness of the film (A) is smaller than 12 μm,mechanical strength of the support film is low and there is a tendencythat the support film is broken in the coating process. If thickness ofthe support film (A) is greater than 25 μm, there is a tendency that theresolution is low and the price is high.

In this invention, the photosensitive resin composition used in thephotosensitive resin composition-containing photosensitive resin layer(B) is not particularly limited, so far as the composition has aphotosensitivity. Preferably used compositions are those comprising:

-   (a) a binder polymer obtained by copolymerizing acrylic acid or    methacrylic acid and alkyl esters thereof as constituent monomers,-   (b) a monomer having at least one polymerizable ethylenically    unsaturated group in the molecule thereof, and-   (c) a photopolymerization initiator.

The binder polymer (a) may be any of a single binder polymer and acombination of two or more binder polymers.

As the alkyl ester of acrylic acid, for instance, methyl acrylate, ethylacrylate, butyl acrylate, 2-ethylhexyl acrylate and the like can bereferred to. These compounds may be used either singly or in combinationof two or more compounds.

As the alkyl ester of methacrylic acid, for instance, methylmethacrylate, ethyl methacrylate, butyl methacrylate, 2-ethylhexylmethacrylate and the like can be referred to. These compounds may beused either singly or in combination of two or more compounds.

The acrylic acid and methacrylic acid mentioned above may be used incombination, if desired.

As the constituent monomer of the binder polymer, not only the acrylicacid, methacrylic acid and alkyl esters thereof but also vinyl monomerscopolymerizable therewith can be used. As the vinyl monomers which areother than the acrylic acid, methacrylic acid and alkyl esters thereofand copolymerizable therewith, for instance, tetrahydrofurfurylacrylate, tetrahydrofurfuryl methacrylate, dimethylaminomethyl acrylate,dimethylaminomethyl methacrylate, glycidyl acrylate, glycidylmethacrylate, 2,2,3,3-tetrfluoropropyl acrylate,2,2,3,3-tetrafluoropropyl methacrylate, acrylamide, diacetoacrylamide,styrene, vinyltoluene and the like can be referred to. These monomerscan be used either singly or in combination of two or more monomers.

The copolymer can be synthesized by mixing together the above-mentionedcomponents and subjecting the mixture to a known polymerization processsuch as solution polymerization process.

The compounding ratio of the above-mentioned constituent monomers is notparticularly limited, but the monomers may be compounded at an arbitraryratio. However, it is preferable from the viewpoint of the balancebetween alkali-developability and alkali-resistance to adjust thecarboxyl group-content of component (a), namely the ratio of carboxylgroup-containing monomers to the total monomers used, to 12 to 40% byweight.

The copolymers thus formed may be used either singly or in combinationof two or more copolymers.

In this invention, the weight-average molecular weight, measured by gelpermeation chromatography and calculated by referring to a standardpolystyrene calibration curve, of the binder polymer (a) in thephotosensitive resin composition-containing photosensitive resin layer(B) is not particularly limited. However, from the viewpoint of thebalance between mechanical strength and alkali-developability, theweight-average molecular weight of binder polymer (a) is preferably inthe range of from 20,000 to 300,000 and further preferably in the rangeof from 40,000 to 200,000. If the weight-average molecular weight islower than 20,000, mechanical strength tends to be low. If the weightaverage molecular weight is higher than 300,000, alkali-developabilitytends to be inferior.

As the monomer (b) having at least one polymerizable ethylenicallyunsaturated group in the molecule thereof used in the photosensitiveresin composition-containing photosensitive resin layer (B) of thisinvention, for instance, there can be referred to the compounds obtainedby reacting a polyhydric alcohol with an α,β-unsaturated carboxylic acidsuch as polyethylene glycol diacrylate having 2 to 14 ethylene units,trimethylolpropane diacrylate, trimethylolpropane triacrylate,tetramethylolmethane triacrylate, tetramethylolmethane tetraacrylate,polypropylene glycol diacrylate having 2 to 14 propylene units,dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate and thelike; bisphenol A polyoxyalkylene diacrylates such as2,2-bis(4-(acryloxydiethoxy)phenyl)propane,2,2-bis(4-(acryloxypentaethoxy)-phenyl)propane,2,2-bis(4-acryloxydiisopropoxytriethoxy)-phenyl)propane, and the like;compounds obtained by adding an α,β-unsaturated carboxylic acid to aglycidyl group-containing compound such as trimethylolpropanetriglycidyl ether triacrylate, bisphenol A diglycidyl ether diacrylateand the like; and alkyl esters of acrylic acid such as methyl acrylate,ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate and the like. Themethacrylates and methacrylic esters corresponding to these compoundscan also be referred to. These compounds can be used alone or as amixture thereof. Among them, the bisphenol A polyoxyalkylenedimethacrylates are preferable from the viewpoint of sensitivity,resolution, adhesiveness and mechanical properties.

As the photopolymerization initiator (c) usable in the photosensitiveresin composition-containing photo-sensitive resin layer (B) of thisinvention, for instance, there can be referred to aromatic ketones suchas benzophenone, N,N′-tetramethyl-4,4′-diaminobenzophenone,N,N′-tetraethyl-4,4′-diaminobenzophenone,4-methoxy-4′-dimethylaminobenzophenone, 2-ethylanthraquinone,phenanthrenequinone and the like; benzoin ethers such as benzoin methylether, benzoin ethyl ether, benzoin phenyl ether and the like; benzoinssuch as methylbenzoin, ethylbenzoin and the like; benzyl derivativessuch as benzyl methyl ketal and the like; 2,4,5-triarylimidazole dimerssuch as 2-(o-chlorophenyl)-4,5-diphenylimidazole dimer,2-(o-chlorophenyl)-4,5-di(m-methoxyphenyl)-imidazole dimer,2-(o-fluorophenyl)-4,5-diphenylimidazole dimer,2-(o-methylphenyl-4,5-diphenylimidazole dimer,2-(p-methoxy-phenyl)-4,5-diphenylimidazole dimer,2,4-di(p-methoxy-phenyl)-5-phenylimidazole dimer,2-(2,4-dimethoxyphenyl)-4,5-diphenylimidazole dimer,2-(p-methylmercaptophenyl)-4,5-diphenylimidazole dimer and the like;acridine derivatives such as 9-phenylacridine,1,7-bis(9,9′-acridinyl)-heptane and the like; phenanthrenequinones suchas 9,10-phenanthrenequinone and the like, etc. Among them, the2,4,5-triarylimidazole dimers are preferable from the viewpoint ofsensitivity and resolution. These photo-polymerization initiators may beused either singly or in combination of two or more compounds.

In the photosensitive resin composition comprising the above-mentionedcomponents (a), (b) and (c), the amount of component (a) is preferablyin the range of from 40 to 80 parts by weight per 100 parts by weight ofthe sum of components (a) and (b). If the amount of component (a) isless than 40 parts by weight, the photo-cured product tends to bebrittle with inferior coating characteristics. If the amount ofcomponent (a) exceeds 80 parts by weight, sensitivity tends to beinsufficient.

In the photosensitive resin composition comprising components (a), (b)and (c), the amount of component (b) is preferably in the range of from20 to 60 parts by weight per 100 parts by weight of the sum ofcomponents (a) and (b). If the amount of component (b) is less than 20parts by weight, sensitivity tends to be insufficient. If the amount ofcomponent (b) exceeds 60 parts by weight, the photo-cured product tendsto be brittle.

In the photosensitive resin composition comprising components (a), (b)and (c), the amount of component (c) is preferably in the range of from0.1 to 20 parts by weight per 100 parts by weight of the sum ofcomponents (a) and (b). If the amount of component (c) is less than 0.1part by weight, sensitivity tends to be insufficient. If the amount ofcomponent (c) exceeds 20 parts by weight, there is a tendency that anincreasing quantity of light tends to be absorbed at the surface ofcomposition at the time of exposure, which brings about an insufficientphoto-cure in the internal regions of the composition.

Into the photosensitive resin composition used in this invention may beincorporated, if necessary, a plasticizer, a thermal polymerizationinhibitor, a color-developer such as leuco-Crystal Violet,tribromomethylphenyl sulfone and the like, a dye such as Malachite Greenand the like, a pigment, a filler, an adhesiveness improver, a perfume,an imaging agent, etc.

The photosensitive resin composition comprising the components (a), (b)and (c) is formed into a photosensitive resin layer (B) by adding asolvent to the composition to prepare a solution, if necessary, and thencoating the solution on a support film (A) and drying the coat. Then, aprotecting film (C) is stuck onto the photosensitive resin layer toprepare a photosensitive film.

The solvent used for this purpose is not particularly limited, but allthe known solvents can be used. Examples of the solvent include acetone,methyl ethyl ketone, methyl isobutyl ketone, ethylene glycol monomethylether, ethylene glycol monoethyl ether, chloroform, methylene chloride,toluene, methanol, ethanol and the like. These solvents may be usedeither as a single solvent or in combination of two or more solvents.

Thickness of the photosensitive resin layer must be in the range of 5 to30 μm. If the thickness is smaller than 5 μm, follow-up characteristicsare deteriorated and defective pattern appears or breakage of wireoccurs. If the thickness is greater than 30 μm, resolution isdeteriorated. Preferable thickness is 10 to 25 μm.

Viscosity (at 30° C.) of the photosensitive resin layer is preferably inthe range of from 15 to 50 MPa·s, and further preferably in the range offrom 25 to 40 MPa·s. If the viscosity is lower than 15 MPa·s at 30° C.,exudation of the resin, called “edge fusion”, tends to occur readily. Ifthe viscosity is higher than 50 MPa·s at 30° C., flow property of theresin is deteriorated which facilitates generation of micro-voids. Theviscosity can be measured by the use of the following equation (I)expressing the behavior of a Newtonian fluid, namely by plotting tagainst 1/Z4 and measuring the slope of the line:

$\begin{matrix}{t = {\eta\;\frac{3V^{2}}{8\pi\; F}\left( {\frac{1}{Z^{4}} - \frac{1}{Z_{0}^{4}}} \right)}} & (1)\end{matrix}$wherein η is viscosity (Pa·s),

F is force applied in the direction of thickness (N),

V is volume of test piece (m³)

Z is thickness (m), and

t is time (second).

The measurement can be practiced by means of TMA apparatus.

The number of fish eyes having a diameter (φ) of at least 80 μm includedin the protecting film used in this invention must be 5/m² or less. Asused herein, the term “fish eye” means unmelted or deteriorated regionof the raw material which has been taken into film at the time ofthermally melting the raw material and forming it into a film bykneading, extrusion, stretching or casting.

Although the diameter of the fish eye varies depending on material, itis from about 10 μm to about 1 mm. The height of the fish eye from filmsurface is from about 1 μm to about 50 μm. The size of fish eye can bemeasured by means of, for instance, optical microscope, contact typesurface roughness meter or scanning electron microscope. The diameter(φ) of fish eye means its maximum diameter.

As to surface roughness of the protecting film, it is preferable thatthe center line-averaged roughness Ra is from 0.005 to 0.05 μm, and itis further preferable that Ra is from 0.01 to 0.03 μm. The surfaceroughness can be measured by means of contact type surface roughnessmeter.

A protecting film of good fish eye level which can successfully be usedin this invention can be produced by modifying the production method offilm, for instance, in such a manner as filtering the raw material resinafter thermal melting.

Some commercially available polypropylene films such as TorayfanBO-2400, YR12 type manufactured by Toray Industries, Inc., ALPHAN E200series manufactured by Oji Paper Co., Ltd. and the like can also bereferred to as examples of the protecting films preferably usable inthis invention, though they are not limitative.

Film thickness of the protecting film (C) is preferably in the range offrom 5 to 50 μm, preferably 5 to 30 μm. If the thickness is smaller than5 μm, such a film tends to be difficult to manufacture. If the thicknessis larger than 50 μm, price of the film tends to be high.

It is preferable that adhesive strength between the photosensitive resincomposition-containing photo-sensitive resin layer (B) and the supportfilm (A) is greater than adhesive strength between the photosensitiveresin composition-containing photosensitive resin layer (B) and theprotecting film (C). If adhesive strength between the photosensitiveresin composition-containing photo-sensitive resin layer (B) and thesupport film (A) is smaller than adhesive strength between thephotosensitive resin composition-containing photosensitive resin layer(B) and the protecting film (C), there is a possibility that thephotosensitive resin layer is transferred onto the protecting film uponremoval of the protecting film at the time of lamination.

The photosensitive film of this invention can be successfully used as aphotosensitive film for metal etching fabrications of lead frame, metalmask, etc.

Next, this invention is explained in more detail with reference toExamples. This invention is by no means limited by these Examples.

EXAMPLES 1-3 AND COMPARATIVE EXAMPLES 1-2

A solution was prepared by mixing together the components (a), (b) and(c) shown in Table 1.

TABLE 1 Amount Material Formulation Formulation 2 Formulation 3Component (a) 40% (by weight) solution of methacrylic 1 1′ 140 g 150 gacid/methyl methacrylate/butyl methacrylate/2- 150 g 160 g (solidcontent (solid content ethylhexyl acrylate copolymer (25/50/5/20 by(solid (solid 56 g) 60 g) weight) having a weight average molecularweight content content of 80,000 in 6/4 (by weight) mixture of methyl 60g) 64 g) cellosolve and toluene Component (b)2,2-Bis(4-methacryloxypentaethoxyphenyl)-propane 40 g  44 g  40 g (tradename BPE-500, manufactured by Shin-Nakamura Kagaku Kogyo K.K.) Component(c) Benzophenone 5 g 0 g N,N′-Tetraethyl-4,4-diaminobenzophenone 0.3 g  0.3 g   2-(o-chlorophenyl)-4,5-diphenylimidazole dimer 0 g 4 g OtherColor Tribromomethylphenyl sulfone 1.0 g   0 g components developerLeuco-Crystal Violet 1.0 g   1.0 g   Dye Malachite Green 0.1 g   0.1 g  Solvent Methyl ethyl ketone 10 g  10 g  Toluene 10 g  10 g  Methanol 3 g3 g

Next, the solution of photosensitive resin composition obtained abovewas uniformly coated onto a polyethylene terephthalate film having athickness of 16 μm and dried for 5 minutes in a hot air circulation typeoven kept at 100° C. Then, each of the protecting films shown in Table 2were laminated thereon to obtain various photo-sensitive films. Afterdryness, thickness of the photo-sensitive resin layer was 15 μm.

The photosensitive films obtained above were superposed so that thephotosensitive resin layers thereof came into mutual contact, to preparea test piece having a thickness of 1 mm and a diameter of 7 mm. Using aIMA apparatus (Thermal Analysis TMA/SS100, manufactured by Seiko DenshiK. K.), a load of 2 to 40 g was applied to the test piece in thedirection of thickness thereof at a temperature of 30 to 80° C., and thechange in thickness was measured. Then, using the equation (I) relatingto Newtonian fluid, t was plotted against 1/Z⁴. Slope of the line gaveviscosity.

$\begin{matrix}{t = {\eta\;\frac{3V^{2}}{8\pi\; F}\left( {\frac{1}{Z^{4}} - \frac{1}{Z_{0}^{4}}} \right)}} & (1)\end{matrix}$

On the other hand, a copper alloy plate having a thickness of 0.15 mmtand a size of 20×20 cm square (trade name C-7025) manufactured byYAMAHA-OLIN METAL Co. was immersed in 3% (by weight) aqueous solution ofsodium hydroxide at 50° C. for one minute and then in a 1% (by volume)aqueous solution of hydrochloric acid at 25° C. for one minute, and thenwashed with water and dried to obtain a substrate. The photosensitivefilm obtained above was laminated on the substrate while removing theprotecting film at a roll temperature of 110° C., under a pressure of 4kg·f/cm², at a speed of 2 m/minute. The laminated substrate thusobtained was exposed to light by means of a 3 kW Super-High PressureMercury Lamp (HMW-201GX, manufactured by ORC Seisakusho, Ltd.) at 50mJ/cm².

After the exposure, the number of air voids on the substrate was countedunder a microscope at a multiplication of 100. Further, the size andnumber of fish eyes on each protecting film were measured under amicroscope at a multiplication of 100.

The results are summarized in Table 2.

TABLE 2 Number of Number of Protecting film fish eyes air voidsRemovability Film thick- (φ ≧ 80 μm) Viscosity generated of protectingNo. Kind ness (μm) (per m²) Formulation (Mpa · s) (per m²) film Example1 GS-16 16 0 1 40 0 ◯ (manufd. by 1′ 55 5 ◯ Teijin, Ltd.) 2 25 0 ◯Example 2 PP-Type PT 25 0 1 40 0 ⊚ (manufd. by Shin- 1′ 55 5 ⊚ Etsu FilmCo.) 2 25 0 ⊚ Example 3 BO-2400 25 0 1 40 0 ⊚ (manufd. by Toray 1′ 55 5⊚ Industries, Inc.) Comparative NF-13 25 ca. 1,000 1 40 ca. 900 ⊚Example 1 (manufd. by 2 25 ca. 500 ⊚ Tamapoly Co.) Comparative PP-Type R25 ca. 1,200 1 40 ca. 1,000 ⊚ Example 2 (manufd. by Shin- Etsu Film Co.)Example 4 E 200C 20 0 1 40 0 ⊚ (manufd. by Oji 1′ 55 3 ⊚ Paper Co.,Ltd.) 3 40 0 ⊚ Note) GS-16: Polyethylene terephthalate film PP-Type PT,PP-Type R, BO-2400, E 200C: Polypropylene film NF-13: Polyethylene film⊚: Excellent - A protecting film was removed from a photosensitive resinlayer smoothly and easily. ◯: Good - A protecting film was removed froma photosensitive resin layer relatively smoothly and easily.

It is apparent from Table 2 that the generation of air voids causingbreakage of wire and appearance of defective pattern can be suppressedby using, as the protecting film (C), a film in which the number of fisheyes having a diameter (φ) of at least 80 μm does not exceed 5/m².

The photosensitive film of this invention reduces the number of airvoids generated which cause occurrence of defective pattern and breakageof wire, and therefore it is quite useful for improvement of productyield in the metallic precision fabrications.

1. A photosensitive film which comprises a support film (A), aphotosensitive resin composition-containing photosensitive resin layer(B) formed on said support film (A), and a protecting film (C) stuckonto said photosensitive resin layer (B), wherein the number of fisheyes having a diameter of 80 μm or more included in said protecting film(C) is zero; and said photosensitive resin composition-containingphotosensitive resin layer (B) has a film thickness of 5 to 30 μm, andwherein said photosensitive resin composition used in saidphotosensitive resin composition-containing photosensitive resin layer(B) comprises: (a) a binder polymer obtained by copolymerizing acrylicacid or methacrylic acid and alkyl esters thereof as constituentmonomers; (b) a monomer having at least one polymerizable ethylenicallyunsaturated group in the molecule thereof; and (c) a photopolymerizationinitiator, said binder polymer (a) having a weight-average molecularweight of from 20,000 to 300,000, and said photosensitive resincomposition comprises component (a) in an amount of from 40 to 60 partsby weight per 100 parts by weight of the sum of components (a) and (b).2. A photosensitive film according to claim 1, wherein the adhesivestrength between the photosensitive resin-composition containingphotosensitive resin layer (B) and the support film (A) is greater thanthe adhesive strength between the photosensitive resincomposition-containing photosensitive resin layer (B) and the protectingfilm (C).
 3. A photosensitive film according to claim 1, wherein thephotosensitive resin layer (B) has a viscosity of 15 to 50 MPa·s at 30°C.
 4. A photosensitive film according to claim 1, wherein the surfaceroughness of said protecting film (C) in terms of the centerline-averaged roughness Ra is 0.005 to 0.05 μm.
 5. A photosensitive filmaccording to claim 1, wherein said protecting film (C) has a thicknessof 5 to 50 μm.